1. Field of the Invention
This invention relates to a fuel injection apparatus and applied to a diesel engine, etc. equipped with an accumulator fuel injection apparatus, the apparatus having a common rail for storing high pressure fuel, the high pressure fuel in the common rail being supplied to fuel injection valves for injecting fuel into each of cylinders of the engine through a plurality of high pressure fuel outlets provided in the common rail equally spaced along longitudinal direction thereof.
2. Description of the Related Art
In the field of diesel engines, an accumulator fuel injection apparatus equipped with a common rail for accumulating high pressure fuel to be injected through injection valves to each of the engine cylinders is widely used in recent years.
In such an accumulator fuel injection apparatus, pulsation of fuel pressure occurs in the common rail due to periodical opening and closing of the fuel injection valves. As the high pressure fuel outlets are provided in the common rail at equal spacing to each other to supply high pressure fuel in the common rail to each of the engine cylinders via each of fuel injection pipes connected to each of the high pressure fuel outlets and fuel is injected at regular intervals, a stationary wave is generated in the common rail, which may affect next fuel injection.
There are disclosed fuel injection apparatuses to reduce such pulsation of fuel pressure for example in Japanese Patent No. 3178105 (patent literature 2) and in Japanese Laid-Open Patent Application No. 11-159372 (patent literature 2).
According to the patent literature 1, a pulsation suppression chamber of a certain volume is provided in a central part in the longitudinal direction of the accumulation chamber of the common rail to suppress fuel pressure pulsation in the accumulation chamber by the effect of the volume of the pulsation suppression chamber, and a common rail pressure sensor is located in the pulsation suppression chamber to detect fuel pressure in the suppression chamber, i.e. average pressure in the common rail.
According to the patent literature 2, an electronic control device calculates corrected fuel injection pressure based on a set value of fuel injection quantity, determines fuel injection pressure based on the calculated injection pressure and determines injection valve opening period taking into consideration the corrected fuel injection pressure. Therefore, even if the fuel pressure pulsation is generated in the fuel injection system due to fuel injection and a phenomenon occurs that reflected pressure wave coincides in phase with injection period of next cylinder, injection valve opening period is controlled taking into consideration expected effect of the reflection pressure wave, so an optimal fuel injection quantity for the engine in its operating condition and fuel pressure pulsating condition can be secured.
It is necessary to detect average fuel pressure in the accumulation chamber accurately without disturbed by the peak and minimum pressure of the pressure pulsation in the accumulation chamber when the fuel pressure in the accumulation chamber is to be used as signals for controlling fuel injection.
According to the art disclosed in the patent literature 1, a pulsation suppression chamber of a certain volume is provided in a central part in the longitudinal direction of the accumulation chamber of the common rail to suppress the fuel pressure pulsation in the accumulation chamber, so the volume of the pressure suppression chamber effects to reduces the rate of pressure rise in the accumulation chamber particularly at engine starting, which may harm engine startability. Further, as the common rail pressure sensor is positioned at the bottom of the pressure suppression chamber formed to extend perpendicularly to the accumulation chamber, responsivity of the common rail pressure sensor to pressure change in the accumulation chamber is reduced.
According to the art disclosed in the patent literature 2, corrected fuel injection pressure is calculated based on the set value of fuel injection quantity using the electronic control device, and fuel injection pressure is corrected based on the calculated injection pressure and fuel injection period is controlled in consideration of the corrected injection pressure. However, there is no teaching concerning the common rail pressure sensor.